patch 8.2.4052: not easy to resize a window from a plugin

Problem:    Not easy to resize a window from a plugin.
Solution:   Add win_move_separator() and win_move_statusline() functions.
            (Daniel Steinberg, closes #9486)
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 1ef4f26..71a4850 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -963,6 +963,8 @@
 	win_gotoid()		go to window with ID
 	win_id2tabwin()		get tab and window nr from window ID
 	win_id2win()		get window nr from window ID
+	win_move_separator()	move window vertical separator
+	win_move_statusline()	move window status line
 	win_splitmove()		move window to a split of another window
 	getbufinfo()		get a list with buffer information
 	gettabinfo()		get a list with tab page information